Electric discharge device



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Nov. 12, 1946. T. M'. LIIMATAINEN ELECTRIC DISCHARGE DEVICE Filed April 21, 1945 Inventor- Toiv'o M. Lpma'bainen, b F

i new a... 12,- rate ELECTRIC DISCHARGE DEVICE Schenectady, N. Y., as-

Toivo M. Liimatainen,

signor to General Elec tion of New York trlc Company, a corpora- Application April 21, 1945, Serial No. 589,487

4 Claims. 1

' My invention relates to electric discharge devices and more particularly to an improved construction for preventing a change in electrical characteristics of the device during manufacture and use. I

In a copending Beggs application, Serial No. 436,633, filed March 28, 1942, and assigned to the assignee of the present invention are described and claimed electric discharge devices particularly adapted for high frequency operation. These devices include a plurality of disk-like high frequency terminals connected with the various electrodes of the device and separated by insulating cylinders. I have found that in the manufacture and operation of devices of this character the electrical characteristics vary over a considerable range. For example, the anode-cathode capacitance in a diode or the grid-cathode capacitance in a triode increases considerably with use. Also, the capacitance between the various elements of the device is modified by the heating which occurs during manufacture of the device so that uniform characteristics are diflicult to obtain. I have found that these variations are due to the deposition of material from the cathode on the insulators separating the various electrodes. In accordance with an important aspect of my invention, I provide improved structure particularly adapted for discharge devices of the above type which substantially prevents the deposition of material on the insulating portions of the envelope, with the result that uniform electrical characteristics are readily obtained in these discharge devices and maintained within small limits throughout the operating life of the devices. In accordance with the illustrated embodiments of my invention, high frequency electric discharge devices of the type employing generally planar electrodes are maintained in spaced relation by generally circular bodies of insulating material, such as glass, and which form portions of the envelope. A generally circular shield is secured to one of the electrode mounts and extends in such a direction with respect to the cathode surface and the exposed wall of the insulator as to intercept substantially all material vaporized from the cathode which would otherwise be deposited on the insulator.

My invention willbe better understood by reference to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. In the drawing, Fig. 1 is an elevational view, in section, of a two-element electric discharge device embodying my invention; Fig. 2 is an elevational view, in section, of a three-element electric discharge device embodying my invention, and

Fig. 3 is an elevational view, in section, of a modified form of my invention applied to a different type of three-element electric discharge device.

Referring now to Figs. 1 and 2 of the drawing, I have shown my invention embodied in electric discharge devices of the type described and claimed in the above-identified Beggs application. In the arrangement shown in Fig. l the device is of the two-element type including a disk-like anode I having a. centrally depressed portion 2 forming the active portion of the anode, The member I is supported in spaced and insulated relation with respect to a cylindrical member 3 by a cylindrical insulator 4 preferably of glass. The member 3 has an inwardly directed flange or disk-like portion 5 to which the lower end of the cylinder 4 is sealed. The lower end of the cylindrical member 3 is closed by a'header 6 having a circular trough portion 1 adapted to receive the lower end of the member 3 and to be secured thereto by a body of fusible material 8. The fusible material may to advantage be solder. The header 6 is provided with a plurality of circumferentially arranged openings 9 centrally located in bosses III each of which receives a body of glass I I for sealing through the header suitable lead-in conductors I2. The portions of the conductors extending outside of the envelope are received in contact prongs I3 carried by a suitable insulating base II which is secured to and positioned with respect to the header 6 by means of a skirt I5 formed integrally with the header and surrounding a portion of the base member II.

The cathode of the device includes a disk-like member I6 supported in closely spaced relation with respect to the depressed portion 2 of the anode by a cathode mount including a tubular supporting member I1 having an outwardly extending flange I8 arranged in closely spaced relation with the lower surface of the flange 5 formed on the cylindrical member 3. The flange I8 of the cathode support is held against a mica insulator I9 interposed between the flange It and the flange 5 by means of certain of the lead-in conductors I2. With this arrangement, high frequency currents are bypassed from the cathode support to the flange 5 which forms an externally accessible high frequency cathode connection. The direct current connection with the cathode is readily made with the terminal prongs associated with certain of the conductors I2. A heater element 20, for supplying heat to the cathode, is arranged concentrically with the tubular supstantially constant. I have found that dl fliculties encountered with prior tube constructions of this haracter are largely eliminated by employing is. suitable shield for protecting the insulator 4,

in th particular embodiment illustrated, from material vaporized from the cathode surface. As indicated in the drawing, a shield in the form of a metallic cylinder 21 has an outwardly directed flange 21 welded or otherwise bonded to the lower surface of the anode disk I. The cylindrical shield is of substantially larger diameter than the cathode l6 and extends slightly below the end of the cathode. This simple and relatively inexpensive structural change has rendered it possibl to obtain far more uniform electrical characteristics than prior discharge devices manufactured from similar parts and these characteristics are maintained throughout the life of the device. The active cathode member l6 may to advantage be supported from the upper end of the tubular member I] by a cylinder 26 of thin metal, such as fernico" foil, which provides a good electrical connection between the cathode and its support and which has relatively low heat conducting capacity.

In the modification shown in Fig. 2, the construction of the device is in general similar to that shown in Fig. 1 except that it is of the three-electrode variety and the shield member is secured to the grid disk or terminal instead of the anode disk. Referring now to Fig. 2, the discharge device includes an anode disk 28, a grid disk 29 and a cathode disk 39 formed integrally with a cylindrical member 3! to which a header 32 is hermetically sealed. The header employed in the arrangement of Fig. 2 also forms th tub base. The anode-grid disks 28 and 29 are separated by a glass cylinder 33, and the grid-cathode disks 29 and 30 are separated by a glass cylinder 34. A cylindrical anode member 35 extends through the anode disk 28 and terminates in a planar surface 36 in the region of the grid disk 29. The grid mesh 31 is bonded to the portion of the disk 29 surrounding a centrally located aperture. The cathode construction is essentially the same as that shown in Fig. 1 and the same reference numerals have been applied to corresponding parts.

In the arrangement shown in Fig. 2 the vaporization shield 39 is of the same shape as employed in the arrangement of Fig. 1 but is secured to the lower side of the grid disk 29 and extends towards the active surface of the cathode.

In Fig. 3 I-have shown my invention applied to the type of high frequency electric discharge devic described and claimed in the copending McArthur and Beggs application, Serial No. 520,240, filed January 29, 1944, and in the copending Beggs application, Serial No. 501,790, filed September 10, 1943. Referring to Fig. 3, the discharge device includes an anode member 40 preferably formed of steel which has been coated with a good conducting material such as copper or silver. The anode includes an active portion 4| of relatively small diameter and a skirt portion 42 of relatively large diameter, these portions being connected by a disk-like portion 43 to which a spacing insulator 44 is sealed. The other end of the insulator 44 is sealed to an outwardly directed flange 45 formed on the upper end of a grid cylinder 46 which forms a portion of the envelope or the device. Th lower end of the cylinder 46 is received in a solder trough 4'! which is sealed to the outer edge of a glass cylinder 48. The inner edge of the cylinder 48 is sealed to the outer cylinder 49 of a cathode assembly which is of th type described and claimed in the copending Beggs application, Serial No. 522,097, filed February 12, 1944, and assigned to the assignee of the present invention.' The cathode proper is a disk-like member 5| and as in the modifications of Figs. 1 and 2 is supported from the sleeve 49 by a thin metal cylinder 52 having good electrical conductivity but forming a heat transfer connection of relatively low thermal capacity. The cathode assembly includes a tubular heat shield 53 within which a heater element 54 is supported. Externally accessible connections for the heater element are provided by the sleeve 49 which is connected to one terminal of the heater by a conductor 55 and by a thimble-like sleeve 55 which is positioned in hermetically sealed relation within the cylinder 49 by a body of glass 51 and connected to the other terminal of the heater element 54 by a conductor 58. The grid mesh 59 is supported between the anode and cathode by a grid cylinder 60 which is secured to the grid supporting cylinder 46 in the desired positional relation with respect to the anode and cathode. In the arrangement shown in Fig. 3, the vaporization shield is in the form of a cylindrical flange similar in shape to that employed in Figs. 1 and 2' but secured to the cathode structure near the region of juncture between the sleeve 49 and the sleeve 52. The outwardly extending flange SI of the shield intercepts material vaporized from the a cathode and prevents the deposit of this material on the inner surface of the glass cylinder 48.

While I haveshown and described particular embodiments of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and I, there- 7 fore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure Letters Patent of the United States is:

1. An electric discharge device comprising a planar cathode and at least one other planar electrode, means providing a metal support and a high frequency terminal for said cathode, a metal support for said other electrode, an envelope for said device comprising at least a portion of said means, and a generally cylindrical insulator sealed between said support and said means, a cylindrical member secured to one of said metal supports within said envelope in conelectrode, a disk-like metal support for said other electrode, an envelope for said device comprising at least a portion of said support and a generally cylindrical insulator having one end sealed to said support, a cylindrical member secured to within said envelope in concentric said support relation with tending from to prevent material vaporized from said cathode from depositing on said insulator.

3. An electric discharge device comprising a cathode and at least one other electrode, a metal support for said other electrode, an envelope for said device comprising at least a portion of said support and a generally cylindrical insulator having one end sealed to said support, a shield member secured to said support within said envelope and extending from said support toward said cathode to prevent material vaporized from said cathode from depositing on said insulator.

said cylindrical insulator and exsaid support toward said cathode 4. An electric discharge device comprising a planar circular cathode and at least one other planar electrode, a disk-like metal support for said other electrode, an envelope for said device comprising at least a portion of said support and a generally cylindrical insulator having one end sealed to said support, a cylindrical member of larger diameter than said cathode secured to said support within said envelope in concentric relation with said cylinder and extending from said support toward said cathode to prevent material vaporized from said cathode from depositing on said insulator.

TOIVO M. ImdATAINEN. 

